<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="https://cdn.staticfile.org/react/16.4.0/umd/react.development.js"></script>
    <script src="https://cdn.staticfile.org/react-dom/16.4.0/umd/react-dom.development.js"></script>
    <!-- 生产环境中不建议使用 -->
    <script src="https://cdn.staticfile.org/babel-standalone/6.26.0/babel.min.js"></script>
</head>

<body>
    <div id="app"></div>




</body>
<script type="text/babel">
    function clock() {
        let c = <span>{new Date().toLocaleDateString() + '' + new Date().toLocaleTimeString()}</span>

        ReactDOM.render(c,app)
    }

    clock();
    setInterval(() => {
        clock();
    }, 1000); 

</script>

</html>